In photography field, a lens device is used to capture light from an object and bring it to a focus on an image sensor in a camera. In conventional cameras, the lens device has a motor, a gear unit, lenses and a rail. The lenses can be moved along the rail by being driven by the motor and the gear unit in order to bring light to a focus on the image sensor. However, the motor, the gear unit and the rail are large and heavy.
In recent years, portable electronic devices, such as smart phones, are equipped with a camera module. If the aforementioned lens device is equipped in the portable electronic device, the portable electronic will be not good in portability. In order to reduce the weight of the lens device, some manufacturers remove the motor, the gear unit and the rail to create an unadjustable lens device. However, the unadjustable lens device only can bring light from an object far away from the electronic device to a focus on the image sensor, so it can not focus clearly on objects that are near. In addition, when taking photos, users may get blurry photos due to camera shake.